The connecting of tool heads such as hammers, sledges, axes and the like is an old and well known art. With changes in the wood handles and the development of new handle materials, many new techniques have been used for bonding the tool head to the tool end section of the handle. Tool heads are generally cast metal implements. Thus, the eyehole for the tool head has varying size and shape tolerances.
Adhesives such as epoxy resins are commonly used to seal the wood tool handle tightly fitted to the tool head with a wedge. The adhesive partially seals the wood against moisture absorption, thereby reducing expansion in the wood. The use of specially molded shapes which require wedges to fix the tool or striking tool to the handle are known such as found in U.S. Pat. No. 3,779,296. This particular technique may also require the use of an adhesive. It is also known to use an adapter to attach tool heads to fiberglass tool handles. See particularly U.S. Pat. No. 4,030,847 and the patents specifically related thereto.
Most recently, tool handles having a molded plastic or synthetic material disposed around a rigid reinforcing rod have become commercially popular. Generally, the tool end section of such handles has been molded in the shape of the tool eyehole. See particularly the U.S. Pat. No. 3,770,033 and U.S. Pat. No. 2,837,381, each of which discloses a core reinforced molded synthetic material tool handle. A connection used in conjunction with a molded synthetic material tool handle is disclosed in U.S. Pat. No. 3,874,433. Here, the connection between a tool head and a handle composed of synthetic material includes the use of a bonding resin, an annular trim collar, and a separate metal filler. This particular type of connection, however, is not well suited to the specific type of core reinforced molded tool handle as described herein.
In another type of connection for the core reinforced molded tool handle, the core projects outwardly from the molded synthetic material and projects into the eyehole of the tool. The annular volume around the rigid core projection is then filled with epoxy resin. However, this prior art connection has proven unsatisfactory in actual use of the tool. In such a prior art structure, the handle begins to flex, that is, has freedom to expand and contract along the core. Thus, there is movement with respect to the tool and epoxy and fracturing of the epoxy occurs at the outer end or tip of the reinforcing core. It is believed that the resolution of forces in such a prior art connection involving the expansion and contraction of the handle on and along the core ultimately causes the failure of the epoxy resin bonding material.
Further structural characteristics of such a core reinforced molded plastic handle have caused fractures within the structure of the outer handle material at the connecting point between the tool head and the handle. For example, the molded plastic material necessarily expands and contracts under different atmospheric conditions. For example, if the handle is used in a warm atmosphere, the material expands. If the handle is then taken into a cold atmosphere, contraction of the molded outer coating results. Also, during use of the tool, the force of the blows and the swinging of the tool produces forces which cause the molded outer cover material to move with respect to the tool head. Such a relative movement will, in time, cause damaging cracks or fissures to form in the handle material.